A police marksman opened fire on a young man eight times in just 2.1 seconds after he was stopped in a car en route to a suspected armed robbery, a court has heard.
Azelle Rodney, 24, was hit in the head and body by six of the bullets after the officer reacted 0.06 seconds - or six hundreths of a second - from when his unmarked police vehicle pulled up alongside, the Old Bailey heard.
Specialist firearms officer Anthony Long, 58, would not have had time to see whether Mr Rodney was doing anything before he came into his sights during the "hard stop" operation, jurors were told.
A detailed analysis of the shooting could be pieced together because it was recorded for training purposes on a hand-held video camera operated by another officer in a police car behind.
Jurors were shown the video which included audio of an unidentified man - not Long - exclaiming "Sweet as... sweet as... sweet as" as the shots rang out.
Now-retired officer Long is on trial at the Old Bailey accused of murdering Mr Rodney on the evening of Saturday April 30 2005 in Hale Lane, Mill Hill, north London.
Opening the case, prosecutor Max Hill QC said Mr Rodney was in the back of the Volkswagen Golf, with two men - Wesley Lovell and Frank Graham - in the front.
The Metropolitan Police had received information that the car contained firearms - possibly a machine gun - and the occupants were on their way to commit an armed robbery, he said.
The officer in charge gave the order for the firearms team to be dispatched to make a "hard stop", forcing the Golf to a halt by boxing it in with four unmarked police vehicles.
Long, who was the front-seat passenger in the unmarked vehicle which came alongside the Golf, opened fire on Mr Rodney at short range and in quick succession through an open window with his police-issue Heckler and Koch G36C Carbine.
Mr Hill told jurors: "The majority of those shots caused fatal injuries to Azelle Rodney, culminating in the final two shots which were fired into the top of Azelle Rodney's head.
"The prosecution say that it was not necessary for Mr Long to open fire upon the Golf and Azelle Rodney. Therefore, we say, Mr Long was not acting lawfully when he opened fire.
"That being so, Mr Long's actions in deliberately killing Azelle Rodney, when it was not necessary to do so, make Mr Long guilty of murder."
The court heard Long, whose call sign was E7, joined the force in 1975 and had 30 years' experience before the fatal shooting.
Mr Hill told the jury to bear in mind that being a police officer is an important - and at times dangerous - job which can also be stressful.
But he said that "with onerous duties there come onerous responsibilities" and it was "imperative" that specialist firearms officers act professionally and take the extreme step of opening fire in a public placeonly when absolutely necessary.
Detailed analysis, which included information from the police cars' incident data recorders, showed that Long opened fire for "some other reason than sheer necessity".
Mr Hill said: "Whether through misjudgment, panic or some other reason, Mr Long opened fire and took another life when the circumstances at the moment he pulled the trigger did not justify him in so doing."
The court heard that the evidence suggested the gap between the car pulling up and Long pulling the trigger of his semi-automatic carbine was 0.06 of a second.
Mr Hill told jurors: "Mr Long opened fire extremely quickly as the Bravo car came to a halt. So quickly, we say, that he cannot have taken any time to observe anything happening inside the Golf before he opened fire."
Before then, Long was two cars behind the Golf so he would not have been able to see Mr Rodney before pulling up beside him, the jury was told.
Mr Hill said: "The time gap from the first shot to the eighth and final shot was 2.1 seconds. He fired the first six shots in just over 1.1 seconds. He then paused for just under three-quarters of a second before firing the seventh and eight shots. When firing, the gap between each pull on the trigger was about two-tenths of a second."
The court heard that Long was firing through an open window of the police car and the closed window and bodywork of the Golf at a distance of no more than two to three metres.
The first two shots missed, with one lodging in the metalwork of the Golf and the other fragmenting as it hit the door frame. The third shot hit Mr Rodney's right upper arm and shoulder. Bullet four hit his back as the victim started to fall.
The next two shots entered his head around his right ear and the final two shots, fired after a pause, went through the top of Mr Rodney's head and travelled down towards the base of his skull, the jury was told.
The court heard that Long's gun was a short-barrelled semi-automatic rifle and therefore the trigger had to be pulled for each shot fired.
Long, who worked in the Metropolitan Police CO19 section and gave an address in Leatherhead, Surrey, denies murder.